Effects of de-inking paper sludge on growth and nutritional status of alder and aspen

Improving our understanding of phosphorus (P) or nitrogen (N) fertilization on growth and nutritional status of two woody colonizer species, alder (Alnus crispa (Has.) Pursh) or aspen (Populus deltoides Marsh.), using de-inking paper sludge (DPS) as an organic soil amendment is an avenue to develop sustainable restoration. Factorial greenhouse experiments were therefore conducted to determine the best combination of DPS and fertilizer on growth and nutritional status of woody species grown in degraded soils. For alder, five level of DPS (0, 20, 40, 60 and 80% DPS) in clay substrate or four levels of DPS (0, 10, 20 and 30% DPS) in sand substrate were studied in combination with three levels of P (0, 0.75 and 1.5 g P kg−1 DPS). Similarly, the same levels of DPS in clay or sand substrates were studied in combination with four levels of N (5, 10 and 15 g N kg−1 DPS) for aspen. For alder, the use of DPS in quantities greater than 30% in substrate without supplemental P caused a reduction in alder growth and leaf N content. However, alder showed reasonable growth and nutrition, regardless of the proportion of DPS in the substrate when P was adjusted to 0.75 g kg−1 DPS (d.w.). For aspen, the addition of DPS without supplemental N decreased growth and leaf N content. However, aspen demonstrated satisfactory growth and nutrition when DPS was included at less than 60% of DPS in the substrate and when substrate N was adjusted to 10 or 15 g kg−1 DPS (d.w.). The results of this study suggest that one time heavy application of DPS constitutes a potentially effective organic amendment for soil restoration purposes, but require additional fertilizers to sustain plant growth and nutrition.